Muffling device for gas discharge

ABSTRACT

Gas discharge muffling device having generally cylindrical body with closed ends, inlet pipe directing gas tangentially into body and outlet pipe exhausting gas from device. Baffle plate divides body into inlet and outlet chambers which communicate with inlet and outlet pipes respectively, conduit connecting inlet and outlet chambers. Splitter plate in inlet chamber restricts rotation of gas in inlet chamber induced by tangential entry of gas. Splitter plate is essentially flat sheet disposed in diametrical plane of cylindrical body and parallel to direction of gas entry.

United States Patent 1 Brown [11] 3,750,841 1 Aug.7, 1973 i 1 MUFFLING DEVICE FOR GAS DISCHARGE [76] inventor: Geoiirey Phillip Brown, 212-1286 W. 14th, Vancouver, British Columbia, Canada 221 Filed: Oct-30,1972

211 Appl.No.:301 ,835

[52] us. c|..; .Q ..181/58 511 men. ..F0ln

[58] FieldoiSearch ..18l/58,56,35,39, l8l/33C [56] References Cited UNITED STATES PATENTS 2,936,844 5/1960 Gill .f. 181/58 Primary Examiner-Richard B. Wilkinson Assistant Examiner-Pat Salce Attorney--Brian J. Wood [57] ABSTRACT Gas discharge muffling device having generally cylindrical body with closed ends, inlet pipe directing gas tangentially into body and outlet pipe exhausting gas from device. Baffle plate divides body into inlet and outlet chambers which communicate with inlet and outlet pipes respectively, conduit connecting inlet and outlet chambers. Splitter plate in inlet chamber restricts rotation of gas in inlet chamber induced by tangential entry of gas. Splitter plate is essentially flat sheet disposed in diametrical plane of cylindrical body and parallel to direction of gas entry.

10 Claims, 4 Drawing Figures IIrI Illlllrl' I 1-11-111"; IIrI lulzllllllirrlllllll.

IIIIIIIIIIIT MUFFLING DEVICE FOR 'GAS DISCHARGE BACKGROUND OF THE INVENTION a typical muffler usually attenuates to a major degree sound within a selected frequency range but passes with little attenuation sound within other frequency ranges. The frequencies that are passed by the muffler lie within particular bands of frequency, hereinafter termed pass bands. Many conventional muffling devices have two major limitations; namely poor back pressure characteristics and wide pass band characteristics. A muffler with high back pressure characteristics reduces the efficiency of scavenging of internal combustion engines and thus reduces engine performance. Some mufflershave a wide pass band characteristic and thus are not effective for muffling the exhaust of the engine which contains frequencies within the pass band frequency. A muffler which has a wide pass band is particularly ineffective for muffling the exhaust of an engine which operates over a wide range of speeds. Thus, desirable characteristics of a muffler include low back pressure so as to maintain effective scavenging, and a narrow pass band to attenuate sound within a wide range of frequencies.

SUMMARY OF THE INVENTION The invention reduces difficulties of prior art muffling devices by providing a muffler which attenuates sound over a relatively wide range of frequencies and at the same time has a relatively low back pressure. The device also tends to filter or disintegrate particles in the gas discharge, and thus serves to some degree as a spark arrester, and thus has particular advantages in environments having high fire risk.

One embodiment of the muffling device includes a body having a generally cylindrical side wall having closed ends and a central longitudinal axis, an inlet pipe to direct gas into the body tangentially relative to the side wall so as to induce rotation in the gas, and an outlet pipe to exhaust gas from the device. A baffle plate extends between the cylindrical side wall and divides the device into inlet and outlet chambers which communicate with the inlet and outlet pipes respectively, a conduit interconnecting the inlet and outlet chambers.

A splitter plate having spaced inner and outer edges is provided in the inlet chamber the outer edge thereof being adjacent the closed end. The inner edge extends into the inlet chamber so that rotation of gas in the inlet chamber induced by tangential entry of gas is restricted by the splitter plate. Gas from the inlet chamber thus flows through the conduit essentially axially into the outlet chamber, from where gas exhausts through the outlet pipe.

A detailed description following related to drawings gives exemplification of preferred embodiment of the invention which,'however, is capable of expression in a structure other than that particularly described and illustrated.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a muffling device according to the invention,

FIG. 2 is a top plan view of the muffling device,

FIG. 3 is a simplified section on 3-3 of FIG. 2, some portions not shown in section,

FIG. 4 is a simplified section on 4-4 of FIG. 1.

DETAILED DISCLOSURE A muffling device according to the invention has a cylindrical side wall 12 having ends closed by end caps 13 and 14. An inlet pipe 16, having a central axis 15, receives gas from a discharge, for instance an exhaust of an engine, the gas entering the pipe in direction of an arrow 17. An outlet pipe 18 extending from the side wall 12 discharges the gas in a direction of an arrow 20 to atmosphere, or a further pipe, (not shown). The cylindrical side wall 12 and the end caps l3and 14 define an interior having a central longitudinal axis 21. As seen in F108. 2 and 4, the inlet and outlet pipes 16 and 18 are disposed tangentially relative to the side wall 12, thus rotation is induced in gas in the device after tangential entry through the pipe 16 the rotation being shown by an arrow 23 (FIG. 4 only).

As seen in FIG. 3 only, a baffle plate 27 having a central opening 29 extends between the cylindrical side wall 12 and divides the interior into an inlet chamber 31 communicating with the pipe 16, and an outlet chamber 33 communicating with the pipe 18. The plate 27 has an outer circumferential flange 35 extending around the plate which serves as a means to secure the plate to the side wall 12, for example by welding. The plate 27 is positioned so that the inlet chamber has a volume different from the outlet chamber so as to increase the range of frequencies attenuated by the muffler, that is to decrease pass band width. The opening 29 is defined by an inner circumferential flange 37, which flange increases stiffness of the plate 27 thus reducing undesirable vibration, and also reduces a coefficient of resistance of the opening 29 for gas flowing through the orifice from the inlet chamber to the outlet chamber in direction of an arrow 39. Such reduction of the coefficient reduces back pressure of the muffler, and thus has particular advantage for use with internal combustion engines. The flange 37 also reduces chances of generating an edge tone when gas passes through the opening 29. A tube 41 has an inner end 43 extending into the inlet chamber and has an outlet end 44 having a flared portion 45. The flared portion 45 has a diameter less than an internal diameter of the cylindrical side wall 12 so as to permit the flared portion to fit within the body. As shown in FIG. 3 the flared portion has a diameter less than internal diameter of the outer flange 35thus permitting the flared portion to be secured to the baffle plate27. The outlet end 44 of the tube 41 communicates with the opening 29 in the baffle, the opening and tube thus providing a conduit for connecting the inlet and outlet chambers.

A splitter plate 51 has an outer edge 53 adjacent the end cap 13 and an inner edge 55 extending into the inlet chamber 31. The splitter plate is an essentially flat sheet disposed within a plane containing the central axis 21. The inner edge 55 is spaced axially from a portion 57 of the inlet pipe 16 closest to the closed end of the inlet chamber, so as to reduce chances of an edge tone being produced by gas passing over the edge 55.

The edge 55 has a pair of spaced slots 59 and 60 defining a central tongue 62, which tongue extends inwards into the inlet end of the tube 41, the slots providing clearance for the tubes so as to prevent metal-to-metal contact.

As best seen in FIG. 4, the splitter plate is parallel to a plane containing the central axis of the inlet pipe 16, so that the gas rotating in the direction of the arrow 23 intercepts the splitter plate after passing through approximately ninety degrees from entry into the inlet chamber. Thus rotation of the gas induced by the tangential entry is essentially restricted by the splitter plate producing a turbulence which results in generally axial flow through the tube 41.

As seen in FIG. 4, the inlet pipe 16 has an inner end 65 which is cut at an angle 67 to the axis 15 to eliminate interference between the flared portion 45 and the pipe 16. If there is no chance of such interference the end 65 can be cut squarely (not shown), that is the angle 67 is 90. The outlet pipe 18 has an inner end 70 cut squarely as shown since there is no risk of interference with internal structure of the outlet chamber 33. The inner ends of both pipes 16 and 18 extend to positions within the body sufficient to permit sealing of the pipes with the cylindrical wall.

OPERATION Gas flowing in the inlet pipe 16 in the direction of the arrow 17 enters the inlet chamber and is induced into rotation by the'tangential entry, the rotation shown by the arrow 23. After flowing at least ninety degrees the rotating gas encounters the splitter plate which essentially restricts the rotation and produces turbulence. The gas leaves the inlet chamber and flows essentially axially through the tube 41 into the outlet chamber which it leaves through the outlet pipe 18.

The muffler also has spark arresting properties and thus can be used in environments having high fire risk. As a spark arrester it can be used in almost any attitude, but would appear to function best when disposed as shown in FIG. 1, i.e. when the axis 21 is generally vertical and the inlet chamber is uppermost. Spark arresting properties are attributed to two characteristics of the muffler as below. Firstly, pulverizing of large hot particles by spinning them in the inlet chamber resulting in high velocity contact with the cylindrical side wall 12. The large hot particles disintegrate on contact making smaller hot particles which, if passed out by the muffler, rapidly burn and self-extinguish on contact with air before causing a fire hazard. Secondly the splitter plate produces turbulence in the inlet chamber which produces spaces containing relatively still air or eddies, the spaces being particularly adjacent the flared portion 45 remote from the inlet pipe 16. These spaces tend to collect particles that are not'passed out of the muffler, thus effectively filtering the particles from the exhaust gases.

Summarising, an important performance characteristic of the device is the relatively low back pressure which is attributed to essential restriction of rotation of gas within the inlet chamber, and to providing the opening 29 with the flange 37 to produce a low coefficient of resistance. Chambers 31 and 32 being of different sizes contribute to produce a relatively narrow pass band.

ALTERNATIVES AND EQUIVALENTS As seen in FIG. 3 the tube 41, the flared portion and the opening 29 serve as a conduit to pass gas from the inlet chamber to the outlet chamber. Other means can be provided, for instance the tube 41 can extend and contact the baffle plate 27, thus eliminating the flared portion 45.

As seen in FIGS. 2 and 4, the outlet pipe 18 is disposed tangentially to the cylindrical side wall and is coplanar with the inlet pipe 16. If required the outlet pipe can be disposed tangentially but within a plane at ninety degrees to the inlet pipe, as shown in broken outline at 72, (FIG. 2 only) a first alternative position of the outlet pipe. A second alternative 73 (FIG. 2 only) is also shown, in which the outlet pipe extends radially from the device. Disposition of the outlet pipe 18 is relatively immaterial and it can be in essentially any position relative to the outlet chamber, which chamber serves as a plenum chamber. As direction of gas leaving a plenum chamber is immaterial, the outlet pipe can, if necessary, be aligned with the central axis 21. The latter position provides minimum attenuation of sound and is the least desirable acoustically, but may be convenient for some installations.

The splitter plate is shown to be disposed in a diametrical plane of the body and parallel to a direction of entry of gases into the inlet chamber. Whilst this is desirable to reduce chances of obtaining an edge tone it is not essential and the plate could be disposed in alternative positions, such as at ninety degrees to direction of entry of gases. If the latter position is used, to reduce chances of obtaining an edge tone the splitter plate can be made narrower so that the inner edge is spaced further from the portion 57 of the inlet pipe. As the low back pressure of the device is attributed to the essential restriction of gas rotation in the inlet chamber, a lower limit of width of the splitter plate is reached when the splitter plate no longer sufficiently reduces rotation of the gas. The central tongue 62 is not essential and the baffle plate could have an inner edge with a rectangular recess to accept the tube, thus eliminating the slots 59 and 60. It is felt that the tongue 62 induces axial flow more effectively in the tube 41 than if it were eliminated.

I claim:

1. A muffling device to reduce noise of a gas discharge, the device having a body including a generally cylindrical side wall having closed ends and a central longitudinal axis, the side wall and ends defining an interior; the device further including an inlet pipe adapted to receive the gas discharge, and to direct gas into the device tangentially relative to the side wall to induce rotation into the gas, an outlet pipe to exhaust the gas from the device, a baffle plate extending between the cylindrical side wall dividing the interior of the device into inlet and outlet chambers which communicate with inlet and outlet pipes respectively, a conduit connecting the inlet and outlet chambers; the device further including:

a. a splitter plate provided in the inlet chamber, the

' plate having outer and inner edges, the outer edge being disposed adjacent a closed end of the inlet portion, the inner edge extending into the inlet chamber, so that rotation of gas in the inlet chamber induced by the tangential entry of gas is essentially restricted by 6 the splitter plate, the gas leaving the inlet chamber plate into the inlet chamber, and an outlet end through the conduit in an essentially axial flow to pass communicating with the opening in the baffle into the outlet chamber from where the gas exhausts plate. through the outlet pipe. 6. A muffling device as defined in claim 5 in which 2. A muffling device as defined in claim 1 in which 5 g. the opening of the baffle plate has an annular b. the splitter plate is an essentially flat sheet disflange so as to reduce coefficient of resistance of posed within a plane parallel to the longitudinal gas flow through the opening, to reduce chances of axis. generating an edge tone and to increase stiffness of 3. A muffling device as defined in claim 2 in which the plate.

c. the splitter plate is disposed in a diametrical plane 7. A muffling device as defined in claim 5 in which of the cylindrical side wall and parallel to a direch. the outlet end of the tube has a flared portion. tion of entry of gases into the inlet chamber. 8. A mufflingdevice as defined in claim 7 in which 4. A muffling device as defined in claim 1 in which i. the flared portion of the outlet end of the tube has d. the inner edge of the splitter plate is spaced from a diameter substantially equal to an internal diamea portion of the inlet pipe closest to the closed end ter of the cylindrical side wall of the device. of the inlet chamber so as to reduce chances of an 9. A muffling device as defined in claim 8 in which edge tone being produced by gas passing over the j. the flared portion of the tube is secured to the bafinner edge fle plate.

5. A muffling device as defined in claim 1 in which 10. A muffiing device as defined in claim 1 in which the conduit includes: k. the inlet pipe extends tangentially from the side e. an opening in the baffle plate, wall of the inlet chamber.

f. a tube having an inlet end extending from the baffle 

1. A muffling device to reduce noise of a gas discharge, the device having a body including a generally cylindrical side wall having closed ends and a central longitudinal axis, the side wall and ends defining an interior; the device further including an inlet pipe adapted to receive the gas discharge, and to direct gas into the device tangentially relative to the side wall to induce rotation into the gas, an outlet pipe to exhaust the gas from the device, a baffle plate extending between the cylindrical side wall dividing the interior of the device into inlet and outlet chambers which communicate with inlet and outlet pipes respectively, a conduit connecting the inlet and outlet chambers; the device further including: a. a splitter plate provided in the inlet chamber, the plate having outer and inner edges, the outer edge being disposed adjacent a closed end of the inlet portion, the inner edge extending into the inlet chamber, so that rotation of gas in the inlet chamber induced by the tangential entry of gas is essentially restricted by the splitter plate, the gas leaving the inlet chamber through the conduit in an essentially axial flow to pass into the outlet chamber from where the gas exhausts through the outlet pipe.
 2. A muffling device as defined in claim 1 in which b. the splitter plate is an essentially flat sheet disposed within a plane parallel to the longitudinal axis.
 3. A muffling device as defined in claim 2 in which c. the splitter plate is disposed in a diametrical plane of the cylindrical side wall and parallel to a direction of entry of gases into the inlet chamber.
 4. A muffling device as defined in claim 1 in which d. the inner edge of the splitter plate is spaced from a portion of the inlet pipe closest to the closed end of the inlet chamber so as to reduce chances of an edge tone being produced by gas passing over the inner edge.
 5. A muffling device as defined in claim 1 in which the conduit includes: e. an opening in the baffle plate, f. a tube having an inlet end extending from the baffle plate into the inlet chamber, and an outlet end communicating with the opening in the baffle plate.
 6. A muffling device as defined in claim 5 in which g. the opening of the baffle plate has an annular flange so as to reduce coefficient of resistance of gas flow through the opening, to reduce chances of generating an edge tone and to increase stiffness of the plate.
 7. A muffling device as defined in claim 5 in which h. the outlet end of the tube has a flared portion.
 8. A muffling device as defined in claim 7 in which i. the flared portion of the outlet end of the tube has a diameter substantially equal to an internal diameter of the cylindrical side wall of the device.
 9. A muffling device as definEd in claim 8 in which j. the flared portion of the tube is secured to the baffle plate.
 10. A muffling device as defined in claim 1 in which k. the inlet pipe extends tangentially from the side wall of the inlet chamber. 